Pneumatic hammer

ABSTRACT

A hammer is provided with a housing accommodating a barrel which is axially movable relative to the housing. The barrel has two portions of different diameter. One portion adjacent to the handle is of a smaller diameter, and the other portion is of a greater diameter. These portions form therebetween a shoulder having the end wall facing the handle. An annular space is provided between the outer surface of the barrel and the inner surface of the housing, and mounted in this annular space on both the first and second portions of the barrel are sealing bushings which are in sealing engagement with the housing so that annular spaces are provided between the outer periphery of the bushings and the inner surface of the housing, and a spring member is mounted between the bushings. The invention is aimed at lowering the vibration level at the hammer handle and at reducing the compressed air leakage.

1 United States Patent 1191 'Goppen et a1.

[ Nov. 18, 1975 PNEUMATIC HAMMER Filed:

Appl. No.1 472,864

US. Cl. 173/134; 173/139; 173/162;

1m. C1. B251) 9/04 Field of Search 173/134, 139, 162; 92/169,

References Cited UNITED STATES PATENTS Hansen 279/19.5 Miller 173/139 X3,605,916 9/1971 Voitsekhovsky et a1 173/139 3,788,404 1/1974 Koudelka173/139 3,792,740 2/1974 Cooley 173/139 FOREIGN PATENTS OR APPLICATIONS1,225,677 4/1960 France 173/134 841,893 6/1952 Germany 1.018.819 11/1975Germany 173/139 Primary Examiner-Ernest R. Purser Assistant Examinerl eslie A. Braun Attorney, Agent, or Fi1 r11-Ho1man & Stern [57] ABSTRACT Ahammer is provided with a housing accommodating a barrel which isaxially movable relative to the housing. The barrel has two portions ofdifferent diameter. One portion adjacentto the handle is of a smallerdiameter, and the other portion is of a greater diameter. These portionsform therebetween a shoulder having the end wall facing the handle. Anannular space is provided between the outer surface of the barrel andthe inner surface of the housing, and mounted in this annular space onboth the first and second portions of the barrel aresealing bushingswhich are in sealing engagement with the housing so that annular spacesare provided between the outer periphery of the bushings and the innersurface of the housing, and a spring member is mounted between thebushings. The invention is aimed at lowering the vibration level at thehammer handle and at reducing the compressed air leakage.

9 Claims, 5 Drawing Figures Byers 173/139 Nell 279/19.5 Bergman....173/134 X Sa1engro.... 173/137 Werstein.... 173/134 X Scott 279/19.5 XNaslund 279/19.3 X Neighom 92/172 US. Patent Nov. 18, 1975 US. PatentNov. 18,1975 Sheet20f2 3,920,086

PNEUMATIC HAMMER BACKGROUND OF THE INVENTION The invention relates topneumatic hammers to be used in mechanical engineering, construction andin other fields.

Known in the prior art are pneumatic hammers comprising a housing havinga barrel mounted therein and axially movable relative thereto so that anannular space is defined between the outer surface of the barrel and theinner surface of the housing, with an air-distribution device and animpact mechanism accommodated in the barrel to ensure reciprocation of ahammer piston, under the action of compressed air, the hammer pistonimparting blows to the shank of a working tool received in the forwardend of the barrel, a handle having a trigger means for controlling thesupply of compressed air into the barrel, the handle being rigidlysecured to the housing, sealing members mounted in the annular spacebetween the housing and the barrel, and guide members between thehousing and the barrel (cf. US Pat. No. 3456744,). In this hammer thesealing members directly contact the inner surface of the housmg.

The above-described prior art pneumatic hammer has the followingdisadvantages:

The sealing members are in contact with both the barrel and housing sothat the misalignment of the barrel relative to the housing is possible,whereby the force is transmitted to the housing by-passing ashockabsorbing member, such as spring which may be provided between thebarrel and the housing.

The sealing members' are prone to rapid wear due to such misalignment,thereby resulting in air leakage.

Due to the frictional engagement between the sealing members and thebarrel on the one hand, and between the sealing members and the housingon the other hand, an intensive transmission of vibrations to thehousing and to the handle of the hammer will take place, whereby theoperator will suffer the unhealthy effect of vibration.

Widely known in the art are also pneumatic hammers, wherein the housingis mounted on the barrel so that a continuous metal-to-metal contactsurface is defined therebetween. This design is deficient in that it isdifficult to align the barrel relative to the housing so that there is amisalignment of the barrel relative to the housing resulting in heavyradial forces applied at the contact surface leading to rapid wear ofthe parts and to air leakage in the case of hammers having ashockabsorbing air cushion.

In addition, the continuous contact surface results in a more intensivetransmission of vibrations to the handle.

In the known pneumatic hammers, the reactive force is absorbed by aspring mounted between the housing and the handle, and the spring shouldbe sufficiently strong due to a great pressure force to be applied tothe handle during the operation. At the same time, it is known that theweaker the spring, the better the system from the point of view of thevibration insulation of the handle.

OBJECTS AND SUMMARY OF THE INVENTION It is the main object of theinvention to'provide a pneumatic hammer having a lowered vibration levelon the handle.

Another object of the invention is to reduce the wear of the parts of apneumatic hammer.

Still another object of the invention is to reduce the air consumptionof the pneumatic hammer.

These and other objects are accomplished due to the fact that in apneumatic hammer comprising a housing having a barrel mounted thereinand axially movable relative thereto so that an annular space is definedbetween the outer surface of the barrel and the inner surface of thehousing, an air-distribution device and an impact mechanism accommodatedin the barrel to ensure reciprocations of a hammer piston under theaction of compressed air, with the hammer piston imparting blows to theshank of a working tool received in the forward end of the barrel, ahandle having trigger means for controlling the supply of compressed airinto the barrel, the handle being rigidly connected to the housing,sealing members mounted in the annular space between the housing and thebarrel, and guide members between the housing and the barrel, accordingto the invention, the barrel mounted in the guide members has twoportions of different diameter, of which the first portion adjacent tothe handle is of a smaller diameter, and the second portion is of agreater diameter, with the shoulder being formed between said portionshaving an end wall facing the handle, the sealing members comprisingbushings mounted on the first and second portions of the barrel so thatan annular space is formed between the outer surface of the bushings andthe inner surface of the housing, and a spring member is mounted betweenthe bushings.

With such embodiments of the hammer, the transmission of vibrations tothe handle is reduced due to the floating arrangement of the sealingmembers (bushings) relative to the housing, and the air leakage is alsoreduced due to the fact that very small radial forces are applied to thebushings so that the wear of the sealing surfaces is minimized. As aresult, the transmission of vibrations from the barrel to the handle isreduced, and the air leakage lowered, whereby the air consumption duringthe operation of the hammer is reduced.

In accordance with the invention, the guide members preferably compriseat least one annular row of guide projections provided on the outersurface of the barrel, with each said row including at least threeprojections. Alternatively, said projections may be provided on theinner surface of the housing.

Such embodiment of the guide members contributes to the reduction of thewear of the contact surfaces since a couple arising from an applicationof the pressure force to the hammer, by the operator, will have agreater arm as compared to that in the hammers a continuous contactsurface between the barrel and the housing.

The dimensions of the projections in the axial and circumferentialdirections are preferably substantially smaller than the diameter of thecontact surface between the projection and the inner surface of thehousing, or between the projection and the outer surface of the barrel.

With such embodiment of the guide members, the transmission of unhealthyvibrations from the barrel to the hammer handle is reduced, and thecooperating surfaces are cleaned from dust and extraneous matter whichmay penetrate into the hammer, whereby the wear of the hammer parts isreduced.

The invention will now be described in detail with reference to theaccompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows a longitudinal section ofa pneumatic hammer according to the invention with the guide projections provided on the outer surface of the barrel;

FIG. 2 shows a longitudinal section of a part of the hammer having theguide projections provided on the inner surface of the housing.

FIG. 3 is an enlarged view of detail A in FIG. 1;

FIG. 4 is a sectional view taken along the line IV IV in FIG. 1; and

FIG. is a sectional view taken along the line VV in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS A pneumatic hammer comprises ahousing 1 (FIG. 1) having a barrel 2 mounted therein and axially movablerelative thereto. The barrel 2 accommodates an air-distribution deviceand an impact mechanism (not shown) which ensure reciprocations of ahammer piston under the action of compressed air, with the hammer pistonimparting blows to a shank 3a of a working tool 3 received in theforward end of the barrel 2.

The pneumatic hammer has a handle 4 provided with trigger means (notshown) for controlling the supply of compressed air, and the handle isrigidly secured to the housing 1. The handle 4 is provided with a pipeconnection 5 for connection of an air hose (not shown), a trigger lever6 and a passage 7 for feeding compressed air into the barrel 2.

The air-distribution device, impact mechanism and trigger means of thehammer may be of any known design, as they do not represent the subjectof the invention and are well known to those skilled in the art.Therefore, these devices will not be described herein.

The barrel 2 is mounted in the housing 1 in such a manner that anannular space 8 is defined therebetween. The barrel 2 has two portionsof different diameter of which a first portion 9 adjacent to the handle4 is of a smaller diameter, and a second portion 10 is of a greaterdiameter. A shoulder 11 is formed between the first portion 9 and thesecond portion 10 of the barrel, with the end wall of the shoulderfacing the handle 4.

Sealing members comprise a bushing 12 slidably mounted on the firstportion 9 of the barrel 2 and a bushing 13 which is mounted in the samemanner on the second portion 10 of the barrel 2, and annular spaces 14and 15 are formed between the outer periphery of the bushings 12 and 13and the inner surface of the housing 2, (FIGS. 1, 3). In order toprovide for a tight sealing, a spacing spring member, such as a spring16 is mounted between the bushings 12 and 13. Under the action of thespring 16, end face 17 of the bushing 12 is urged against an end wall 18of the housing 1, and end face 19 of the bushing 13 is urged against anelastic sealing ring 20 which rests against a projection 21 of thehousing I. It should be noted that the end face 17 may engage thehousing 1 through the interposition of an elastic member (not shown).Therefore, a closed chamber is provided in the annular space 8 to supplythe impact mechanism of the hammer with compressed air.

It should also be noted that the sealing ring 20 is mounted with aradial play 22 with respect to the bushing 13 so as not to hamper itsradial displacement when the barrel 2 comes out of alignment with thehousing ll.

The bushings l2 and 13 may be sealed relative to the housing 1 by otherappropriate methods.

The floating arrangement of the sealing bushings l2 and 13 relative tothe housing 1 permits the relieving of the bushings from radial loads,whereby their wear is substantially reduced, and hence air leakage islowered. The air consumption is thereby reduced by 15 30%.

In order to guide the barrel 2 in the housing 1, there are provided onthe outer surface of the barrel 2 two annular rows aa and b-b (FIG. 1)of guide projections 23 cooperating with the inner surface of thehousing 1. The dimensions c and d of the projections in the axial andcircumferential directions, respectively, are substantially smaller thanthe diameter D of the contact surface between the projections 23 and theinner surface of the housing 1. The expression substantially smallermeans herein that the circumferential spacing of the projections 23 issubstantially greater than their dimension d in the circumferentialdirection, while the dimension c is substantially equal to the dimensiond. As an example, it might be indicated that the dimension d is withinthe range of from 0.05 to 0.5 D, while the dimension c may be equal tothe dimension d.

The guide projections 23 may be provided on the inner surface of thehousing 1 as shown in FIG. 2. In this case, the dimensions 0 and d ofthe projections in the axial and circumferential directions,respectively, are substantially smaller than the diameter D of thecontact surface between the projections 23 and the outer surface of thebarrel 2.

This embodiment of the guide members permits the reduction of thetransmission of vibrations to the housing (handle) of the hammer. Inaddition, this results in an increase in the arm of a couple arisingfrom application of the pressure force to the hammer by the operator,whereby the radial load applied at the contact between the guideprojections and the housing is reduced, thereby minimizing the wear ofthese parts. Small dimensions of the guide projections also ensure thecleaning of the contact surface from dust and extraneous matters whichmay penetrate inside the hammer.

In order to improve the efficiency of the vibration insulation, as wellas to ensure the safety and convenience of the control of the workingtool, the pneumatic hammer is provided with means for fixing the workingtool which is described in greater details in our co-pending applicationSer. No. 472,858.

The working tool 3 has the shank 3a, and provided between the workingportion of the tool 3 and the shank 3a, there is a shoulder 24 (FIGS. 1,5) defined by a cone 25 having flats 26 and inclined bearing surfaces27. The working tool 3 is mounted in a cup member 28 and extends througha non-circular opening 29 in the end wall thereof, with the shape of theopening corresponding to the cross-sectional shape of the workingportion of the tool 3, and the shank 3a of the working tool 3 isreceived in a guide sleeve 30 fixed in the barrel 2.

In order to prevent the working tool 3 from being shot off where thereis no contact between the tool and a workpiece, or in the case of anincidental starting of the hammer, there is provided, on the forward endof the barrel 2, a lock 31 comprising a nut screwed on the barrel 2. Theforward end of the lock 31 is tapered and has an opening 32 whose shapecorresponds to the cross-sectional shape of the tool 3 so that the twomay pass through the opening 32 with a predetermined relative angularposition of the openings 29 and 32. For

that purpose, the cup member 28 is provided with a pin 33 (FIGS. 1, 4)which is rotatably mounted in a Circular slot 34 of the cup 28. One endofthe pin 33-.is received in a longitudinally extending groove 35,0f thelock 31 so that upon rotating the pin 33 the lock 31 will be rotated,whereby the operator can bring the openings 29 and 32 in registertowithdrawn the working tool 3 from j the outer surface of the cupmemberj28.

The above-described means for fixing the workin tool 3 in the pneumatichammer enables the-control of the tool during operation by rotating the'cup' member 28, prevents the tool from being shot off during idle blowsof the hammer piston, andprovides for an additional vibration insulationsincethe cup member 28, which is held .by the operator during theoperation with the hammer, does not directly contact the barrel 2 and ismounted on the vibration insulated housing 1 of the hammer. Furthermore,the cup member 28 may be provided with a rubbercoat or covering 39(FIGS. 1,5) for' additional protection of the operator against high.frequency vibration components.

The above-described hammer functions asfollows:

Upon pressing the lever 6 compressed air is fed, into the chamber 8formed between the housing 1 and the barrel 2 andsealed by means of thebushings l2,v 13,

from which the air is fed through the air-distribution device to theimpact mechanism of the hammer (not shown). By that time, the tool 3 ispressed against a workpiece, while the hammer is :held by the operatorgripping the handle 4. During operation, the operator controls theworking tool with the other hand by means of the cup member 28 havingthe rubber coat 39.

The compressed air, which is permanently present in the annular space 8between the housing 1 and the barrel 3, exerts a pressure upon theshoulder 11 of the barrel 2 between the portion 9 of a smaller diameterand the portion 10 of a greater diameter, whereby a permanentshock-absorbing air cushion is formed.

During operation of the impact mechanism the barrel 2 performs areciprocatory motion relative to the housing 1 with a small amplitudeand at a frequency which is substantially equal to the frequency of thereciprocations of the hammer piston (not shown) in the barrel 2. Thevibrations arising therefrom acts upon the operator through the spring16 and the air cushion action on the shoulder 11.

Due to the fact that the spring 16 exerts a comparatively lowcompressive force, as well as due to the presence of the shock-absorbingair cushion acting on the shoulder 11, the handle 4 is very efficientlyinsulated against vibration. This effect becomes more pronounced due tothe fact that the sealing bushings float relative to the housing 1,whereby the transmission of vibrations to the handle 4 is additionallyreduced.

Vibrations generated due to the cooperation between the working tool 3and the barrel 2 is transmitted to the housing 1 through the guideprojections 23 having small dimensions, which also contributes to thereduction of the unhealthy effect of vibrations on the operator.

In addition, it should be noted that since the cup member 28 does notcontact the barrel 2 and the tool 3; the vibrations arising in this Zoneof the hammer will not be transmitted to the hand of the operatorgripping the cup member 28 to control the tool.

Dust and extraneous material penetrating inside the hammerduringoperation will pass between the guide projections 23 so that they willnot result in excessive wear of v the. latter.

It will beapparent from the above description that the pneumatic hammeraccordingtothe invention has lowered the vibration level at the handle,reduced wear of the parts and small air consumption.

While the specific embodiment of the pneumatic hammer according to theinvention was given hereinabove as an .illustrative example, it will beapparent that those skilled in the artcan introduce variousmodifications without departing from the spirit and scope of theinvention as defined in the appended claims.

What is claimed is:

1. A pneumatic. hammer comprising: a housing having an inner surface; abarrel mounted in said housing and axially movable relative thereto;said barrel having a forwardend and an outer surface; anair-distribution device and an impact mechanism accommodated in saidbarrel to ensure reciprocations of a hammer piston under the action ofcompressed air, with the hammer piston imparting blows to a shank of aworking tool received in the forward end of said barrel; the outersurface of said barrel and the inner surface of said housing defining anannular space therebetween; a handle having trigger means forcontrolling the supply of compressed air into said barrel, the handlebeing rigidly secured to said housing; a first portion of said barrelhaving a smaller diameter adjacent to said handle; a second portion ofsaid barrel having a greater diameter; a shoulder formed between saidfirst and second portions of the barrel, an end wall of said shoulderfacing said handle; sealing members comprising bushings mounted on saidfirst and second portions of said barrel; said bushings having outerperipheries and end faces, the end faces being in sealing engagementwith the housing, annular spaces provided between the outer periphery ofsaid bushings and the inner surface of said housing; a spring membermounted between said bushings; and guide members between said housingand said barrel, whereby said sealing members are relieved from theradial load, so that their wear is reduced, as well as compressed airleakage.

2. The pneumatic hammer according to claim 1, wherein said guide memberscomprise at least one annular row of guide projections provided on theouter surface of said barrel, with said row including at least threeprojections.

3. The pneumatic hammer accoording to claim 2, wherein the dimensions ofsaid projections in the axial and circumferential directions aresubstantially smaller than the diameter of the contact surface betweenthe projection and said housing.

4. The pneumatic hammer according to claim 1, wherein said guide memberscomprise at least one annular row of guide projections provided on theinner surface of said housing, with said row including at least threeprojections.

5. The pneumatic hammer according to claim 4, wherein the dimensions ofsaid projections in the axial and circumferential directions aresubstantially smaller than the diameter of the contact surface betweenthe projection and said barrel.

6. A pneumatic hammer comprising: a housing having an inner surface; abarrel mounted in said housing and axially movable relative thereto;said barrel having a forward end and an outer surface; anair-distribution device and an impact mechanism accommodated in saidbarrel to ensure reciprocations of a hammer piston under the action ofcompressed air, the hammer piston imparting blows to a shank of aworking tool received in the forward end of said barrel; the outersurface of said barrel and the inner surface of said housing forming anannular space therebetween; a handle having a trigger means forcontrolling the supply of compressed air into said barrel, said handlebeing rigidly secured to said housing; a first portion of said barrelhaving a smaller diameter adjacent to said handle; a second portion ofsaid barrel having a greater diameter; a shoulder formed between saidfirst and second portions of the barrel, an end wall of said shoulderfacing said handle; sealing members comprising bushings mounted on saidfirst and second portions of said barrel; said bushings having outerperipheries and end faces, the end faces being in sealing engagementwith the housing, annular spaces formed between the outer periphery ofsaid bushings and the inner surface of said housing; a spring membermounted between said bushings; at least one annular row of guideprojections provided on the outer surface of said barrel, with said rowincluding at least three projections, whereby the sealing members arerelieved from the radial load so that their wear is reduced, as well ascompressed air leakage.

7. The pneumatic hammer according to claim 6, wherein the dimensions ofsaid projections in the axial and circumferential directions aresubstantially smaller than the diameter of the contact surface betweenthe projection and said housing.

8. A pneumatic hammer comprising: a housing having an inner surface; abarrel mounted in said housing and axially movable relativethereto;'said barrel having a forward end and an outer surface; anair-distribution means and an impact mechanism accommodated in saidbarrel to ensure reciprocations of a hammer piston under the action ofcompressed air, the hammer piston imparting blows to a shank of aworking tool received in the forward end of said barrel; the outersurface of said barrel and the inner surface of said housing forming anannular space therebetween; a handle having trigger means forcontrolling the supply of compressed air into said barrel, said handlebeing rigidly secured to said housing; a first portion of said barrelhaving a smaller diameter adjacent to said handle; a second portion ofsaid barrel having a greater diameter; a shoulder formed between saidfirst and second portions of said barrel, an end wall of said shoulderfacing said handle; sealing members comprising bushings mounted on saidfirst and second portions of said barrel; said bushings having outerperipheries and end faces, the end faces being in sealing engagementwith said housing, annular spaces provided between the outer peripheryof said bushings and the inner surface of said housing; a spring membermounted between said bushings; and at least one annular row of guideprojections provided on the inner surface of said housing, with said rowincluding at least three projections, whereby the sealing members arerelieved from the radial load so that their wear is reduced, as well ascompressed air leakage.

9. The pneumatic hammer according to claim 8, wherein the dimensions ofsaid projections in the axial and circumferential directions aresubstantially smaller than the diameter of the contact surface betweenthe projection and said barrel.

1. A pneumatic hammer comprising: a housing having an inner surface; abarrel mounted in said housing and axially movable relative thereto;said barrel having a forward end and an outer surface; anair-distribution device and an impact mechanism accommodated in saidbarrel to ensure reciprocations of a hammer piston under the action ofcompressed air, with the hammer piston imparting blows to a shank of aworking tool received in the forward end of said barrel; the outersurface of said barrel and the inner surface of said housing defining anannular space therebetween; a handle having trigger means forcontrolling the supply of compressed air into said barrel, the handlebeing rigidly secured to said housing; a first portion of said barrelhaving a smaller diameter adjacent to said handle; a second portion ofsaid barrel having a greater diameter; a shoulder formed between saidfirst and second portions of the barrel, an end wall of said shoulderfacing said handle; sealing members comprising bushings mounted on saidfirst and second portions of said barrel; said bushings having outerperipheries and end faces, the end faces being in sealing engagementwith the housing, annular spaces provided between the outer periphery ofsaid bushings and the inner surface of said housing; a spring membermounted between said bushings; and guide members between said housingand said barrel, whereby said sealing members are relieved from theradial load, so that their wear is reduced, as well as compressed airleakage.
 2. The pneumatic hammer according to claim 1, wherein saidguide members comprise at least one annular row of guide projectionsprovided on the outer surface of said barrel, with said row including atleast three projections.
 3. The pneumatic hammer accoording to claim 2,wherein the dimensions of said projections in the axial andcircumferential directions are substantially smaller than the diameterof the contact surface between the projection and said housing.
 4. Thepneumatic hammer according to claim 1, wherein said guide memberscomprise at least one annular row of guide projections provided on theinner surface of said housing, with said row including at least threeprojections.
 5. The pneumatic hammer according to claim 4, wherein thedimensions of said projections in the axial and circumferentialdirections are substantially smaller than the diameter of the contactsurface between the projection and said barrel.
 6. A pneumatic hammercomprising: a housing having an inner surface; a barrel mounted in saidhousing and axially movable relative thereto; said barrel having aforward end and an outer surface; an air-distribution device and animpact mechanism accommodated in said barrel to ensure reciprocations ofa hammer piston under the action of compressed air, the hammer pistonimparting blows to a shank of a working tool received in the forward endof said barrel; the outer surface of said barrel and the inner surfaceof said housing forming an annular space therebetween; a handle having atrigger means for controlling the supply of compressed air into saidbarrel, said handle being rigidly secured to said housing; a firstportion of said barrel having a smaller diameter adjacent to saidhandle; a second portion of said barrel having a greater diameter; ashoulder formed between said first and second portions of the barrel, anend wall of said shoulder facing said handle; sealing members comprisingbushings mounted on said first and second portions of said barrel; saidbushings having outer peripheries and end faces, the end faces being insealing engagement with the housing, annular spaces formed between theouter periphery of said bushings and the inner surface of said housing;a spring member mounted between said bushings; at least one annular rowof guide projections provided on the outer surface of said barrel, withsaid row iNcluding at least three projections, whereby the sealingmembers are relieved from the radial load so that their wear is reduced,as well as compressed air leakage.
 7. The pneumatic hammer according toclaim 6, wherein the dimensions of said projections in the axial andcircumferential directions are substantially smaller than the diameterof the contact surface between the projection and said housing.
 8. Apneumatic hammer comprising: a housing having an inner surface; a barrelmounted in said housing and axially movable relative thereto; saidbarrel having a forward end and an outer surface; an air-distributionmeans and an impact mechanism accommodated in said barrel to ensurereciprocations of a hammer piston under the action of compressed air,the hammer piston imparting blows to a shank of a working tool receivedin the forward end of said barrel; the outer surface of said barrel andthe inner surface of said housing forming an annular space therebetween;a handle having trigger means for controlling the supply of compressedair into said barrel, said handle being rigidly secured to said housing;a first portion of said barrel having a smaller diameter adjacent tosaid handle; a second portion of said barrel having a greater diameter;a shoulder formed between said first and second portions of said barrel,an end wall of said shoulder facing said handle; sealing memberscomprising bushings mounted on said first and second portions of saidbarrel; said bushings having outer peripheries and end faces, the endfaces being in sealing engagement with said housing, annular spacesprovided between the outer periphery of said bushings and the innersurface of said housing; a spring member mounted between said bushings;and at least one annular row of guide projections provided on the innersurface of said housing, with said row including at least threeprojections, whereby the sealing members are relieved from the radialload so that their wear is reduced, as well as compressed air leakage.9. The pneumatic hammer according to claim 8, wherein the dimensions ofsaid projections in the axial and circumferential directions aresubstantially smaller than the diameter of the contact surface betweenthe projection and said barrel.